Electro-Magnetic Interference (EMI) is a common problem in the applications of integrated circuits. The EMI becomes a more severe issue in the applications in which high frequencies are used, for example, in mobile applications in which Radio Frequency (RF) signals are used.
To reduce the EMI between device dies, metal shielding cases are used to shield the device dies. The metal shielding cases are typically formed of iron using stamping process. The metal shielding cases are designed to fit the sizes and the shapes of the device dies that are to be shielded. After the dies are bonded to a Printed Circuit Board, the metal shielding cases are covered on the dies, and are soldered to the PCB. The metal shielding cases provide a two-way shielding, and prevent the dies from interfering with the devices outside of the shielded dies, and prevent the outside devices from interfering with the devices in the shielded dies.
In the conventional metal shielding scheme, the metal shielding cases have to be customized to the shapes and the sizes of dies. With multiple dies on a PCB, which dies have different sizes, a plurality of metal shielding cases with different design is needed. This results in a significant increase in the manufacturing cost of integrated circuits.